Transformer strip winding

ABSTRACT

A transformer winding comprising a strip or foil conductor having two longitudinal fold portions which are folded against the length of the strip. The fold portions have opposed, spaced apart, facing edges which define a space between the edges. The conductor is insulated by an insulative strip which is also folded and has edges overlapped within the space defined by the opposed edges of the strip conductor.

United States Patent [72] Inventor John L. Fisher Lexington, Ky. [21] Appl. No. 104,656 [22] Filed Jan. 7,1971

Jan. 11, 1972 McGraw-Edison Company Elgin, Ill.

[45] Patented [73) Assignee [54] TRANSFORMER STRIP WINDING 12 Claims, 3 Drawing Figs.

[521 11.8. CI 336/206, 156/50, 156/54, 174/119 R. 336/223 [51] lnt.Cl H0li27/28 [50] Field 01 Search .4 336/206,

241 .53 jg, m A: QQL N [56] References Cited UNITED STATES PATENTS 753,461 3/1904 Anderson 174/117 FF 3,402,255 9/1968 Parker 174/133 B FOREIGN PATENTS 687,971 6/1964 Canada 174/117 R 638,025 5/1950 Great Britain .7 174/117 F Primary Examiner- Thomas J. Kozma AttorneyRichard Ct Ruppin TRANSFORMER STRIP WINDING BACKGROUND OF THE INVENTION This invention relates to an electrical strip winding and, in particular, to an insulated strip conductor for a transformer winding.

In recent years, transformer windings wound from strip or foil conductive material have become increasingly popular due to the ease with which strip material may be wound. Because of the generally rectangular or flat thin cross section of strip conductors, windings using such conductors have minimal space factor loss and also have a great deal of mechanical strength. However, obtaining these advantages depends to a large degree on the insulation arrangement of the conductors. Also, the conductors must be adequately insulated from each other and the necessary insulation arrangement may minimize the aforementioned advantages.

SUMMARY OF THE INVENTION It is a general object of the invention to provide an insulated strip conductor having substantially flat sides and in which an insulation strip surrounds a conductive strip and has over lapping portions along a flat side of the conductive strip. The objects of the invention are accomplished by providing a con ductive strip having opposite edges folded toward the central portion of the strip with each ofthe folded portions having opposed, spaced apart facing edges. A strip of insulative material is folded around the conductive strip and has overlapping edges with one of the edges being positioned in the space defined by the opposed edges of the conductive strip so that the overlap occurs substantially in the defined space. Thus, the insulated conductor has two substantially flat sides even though its insulation covering is overlapped on one of the sides.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 shows a transformer winding incorporating the insulated strip conductor according to the instant invention;

FIG. 2 illustrated the insulated conductor after a step in the method ofits making; and

FIG. 3 shows a cross-sectional view of the insulated conductor in final form.

DESCRIPTlON OF THE PREFERRED EMBODIMENT Referring to the drawings in greater detail and in particular to FIG. 1, a transformer having a core 2 is shown to include a low-voltage winding assembly 4 wound on a core tube 6 and a high-voltage winding assembly 8 concentrically wound on the low-voltage winding assembly 4. An insulating barrier 10 separates the low-voltage winding assembly 4 and the highvoltage winding assembly 8. The low-voltage winding assembly 4 is wound from a full width insulated strip conductor 12. The insulated strip conductor 14 of the high-voltage winding assembly 8 may also comprise the full width of the winding assembly 8 or the winding assembly 8 may comprise a series of axially displaced spirally wound sections of strip conductor 14 each having a toroidal shape.

A cross-sectional view of the high-voltage strip conductor 14 is shown in FIG. 3. The insulated strip conductor 14 includes a conductive strip 20. The conductive strip has a flat portion 22 and two fold portions 24 and 26. The conductive strip 20 is of a generally rectangular cross section and has wide surfaces 28 and 30 and outwardly facing longitudinal edges 32 and 34. The fold portions 24 and 26 are bent along lines parallel to the edges 32 and 34 and respectively have opposed facing edges 38 and 36 which form a space or groove 40 running parallel to edges 32 and 34.

The high-voltage insulative strip conductor 14 also includes an insulative strip 50 having a flat portion 52 and fold portions 54 and 56. The insulative strip 50 is positioned around and in engagement with conductive strip 20 with the fold portions 54 and 56 respectively engaging the fold portions 24 and 26 of the conductive strip 20. As shown in FIG. 3, the insulative strip 50 may also be considered to be in the form of a rectangular tube surrounding the conductive strip 20. The fold portions 54 and 56 respectively have overlapping edges 58 and 60. The overlapping engagement of the edges 58 and 60 is in the space between the facing edges 36 and 38 of the cond uctive strip fold portions 24 and 26 and the overlapped edge 58 of the fold portion 54 extends into the space or groove 40. As seen in FIG. 3, where the thickness of insulative strip 50 is not greater than that of conductive strip 20, overlapping of edges 58 and 60 in the space defined by facing edges 36 and 38 per mits the fold portions 54 and 56 which are not overlapped to be in the same plane so that the fold portions together also comprise a substantially flat side of the strip conductor 14.

The steps of making the insulated strip conductor 14 include the positioning ofa conductive strip 20 on an insulative strip 50 that the latter extends beyond the edges of the con ductive strip 20, as shown in FIG. 2, and adhering the conductive strip 20 to the insulative strip 50. The adhered strips 20 and 50 may then be folded along dashed fold lines 62 and 64 which are located such that the edges of the conductive strip 20 will face each other but be spaced apart subsequent to folding to form the space or groove 40. The width of the insulative strip 50 relative to the width of the conductive strip 20 and the position of the fold lines 62 and 64 must also be such that the edge 58 as shown in FIG. 3 will fit into the groove 40 and the edge 60 will terminate along the overlapped and engaged portion of edge 58. Either subsequent to the folding of the fold portion 54 of the insulative strip 50 or as part of that fold step, the overlapped edge 58 is inserted into the groove 40 and fold ing of fold portion 56 is completed and the overlapped edge 60 is positioned against the edge 58.

it may be readily appreciated from the foregoing description that the entire conductive strip 20 is insulated by the insulative strip 50 and the overlapped edges 58 and 60 of the insulative strip 50 provide an insulating creepage distance to adjacent conductors. Moreover, because the wide surfaces of the insulative strip conductor 14 are flat, no uneven buildup occurs when the strip conductor 14 is wound in a toroidal shape. With the edges of the conductive strip 20 being fully insulated. the wound strip conductor 14 presents a firm coil edge which may engage adjacent coil edges or transformer insulation to support the coils in position. Where the insulated strip conductor i4 is wide relative to the width of the space between facing edges 36 and 38, there is negligible space factor loss due to this space.

While only the preferred embodiment of the invention has been shown herein, it will be realized that modifications thereof are feasible without departing from the spirit and scope of the invention. It is accordingly intended that the scope of the invention is not to be limited to the specific embodiment disclosed.

Iclaim:

1. In a transformer including a winding having a conductor comprising:

an electrically conductive strip having a length including outwardly facing longitudinal edges and two folded portions positioned parallel with said length, said folded portions each having a fold bend positioned at a different one of said outwardly facing edges and having opposed spaced apart facing edges defining a space therebetween; and

an electrically insulative strip having a length positioned against the length of the conductive strip and two folded portions positioned against the folded portions of the con ductive strip, said insulative strip folded portions having edges overlapped in the space between said facing edges of the conductive strip.

2. The combination according to claim 1 wherein said conductive strip and insulative strip are laminated to each other.

3. The combination according to claim I wherein one of said overlapped edges is entirely positioned in said space.

4. The combination according to claim 3 wherein the conductive strip and insulative strip each have a thickness and the thickness of the conductive strip is at least as large as the thickness of the insulative strip.

5. The combination according to claim 3 wherein the balance of the insulative strip folded portions are in the same plane.

6. The combination according to claim 3 wherein the conductive strip folded portions engage the length of the conductive strip.

7. The combination according to claim 3 wherein:

said transformer includes a core and a low-voltage winding around and adjacent the core; and

said conductor is spirally wound around the outside of the low-voltage winding and has a toroidal shape.

8. A transformer winding having a conductor comprising:

a rectangular strip of conductive material having a wide sur face, a length and a groove parallel to said length in the surface; and

a rectangular tube of insulative material positioned around and in engagement with the rectangular strip, said tube having a longitudinal seam comprising two overlapped edges of the insulation material. one of said edges being positioned in said groove.

9. The combination according to claim 8 wherein the other of said overlapped edges engages a portion of the edge in said groove and terminates along said engaged portion.

10. The combination according to claim 8 wherein said rectangular tube is adhered to said rectangular strip.

11. The method of forming an insulated strip conductor for a transformer from an electrically conductive strip having a predetermined width and an electrically insulative strip having a greater width comprising the steps of:

positioning the conductive strip against the insulative strip with the longitudinal edges of the conductive strip spaced from and parallel to the longitudinal edges of the insulative strip; folding two portions of the conductive strip in the same direction against itself along two lines parallel to the longitudinal edges of the conductive strip and spaced apart a distance greater than one-half of the total strip width, whereby a space is defined between facing edges of the fold portions; folding one portion of the insulative strip substantially along one of said two lines against a fold portion of the conductive strip and positioning an edge of said one portion in said defined space; and folding another portion of the insulative strip substantially along the other of said two lines against the other fold portion of the conductive strip and positioning the edge of said other fold portion against the edge of said one fold portion. 12. The method according to claim 11 further comprising the step of adhering the conductive and insulative strips together. 

1. In a transformer including a winding having a conductor comprising: an electrically conductive strip having a length including outwardly facing longitudinal edges and two folded portions pOsitioned parallel with said length, said folded portions each having a fold bend positioned at a different one of said outwardly facing edges and having opposed spaced apart facing edges defining a space therebetween; and an electrically insulative strip having a length positioned against the length of the conductive strip and two folded portions positioned against the folded portions of the conductive strip, said insulative strip folded portions having edges overlapped in the space between said facing edges of the conductive strip.
 2. The combination according to claim 1 wherein said conductive strip and insulative strip are laminated to each other.
 3. The combination according to claim 1 wherein one of said overlapped edges is entirely positioned in said space.
 4. The combination according to claim 3 wherein the conductive strip and insulative strip each have a thickness and the thickness of the conductive strip is at least as large as the thickness of the insulative strip.
 5. The combination according to claim 3 wherein the balance of the insulative strip folded portions are in the same plane.
 6. The combination according to claim 3 wherein the conductive strip folded portions engage the length of the conductive strip.
 7. The combination according to claim 3 wherein: said transformer includes a core and a low-voltage winding around and adjacent the core; and said conductor is spirally wound around the outside of the low-voltage winding and has a toroidal shape.
 8. A transformer winding having a conductor comprising: a rectangular strip of conductive material having a wide surface, a length and a groove parallel to said length in the surface; and a rectangular tube of insulative material positioned around and in engagement with the rectangular strip, said tube having a longitudinal seam comprising two overlapped edges of the insulation material, one of said edges being positioned in said groove.
 9. The combination according to claim 8 wherein the other of said overlapped edges engages a portion of the edge in said groove and terminates along said engaged portion.
 10. The combination according to claim 8 wherein said rectangular tube is adhered to said rectangular strip.
 11. The method of forming an insulated strip conductor for a transformer from an electrically conductive strip having a predetermined width and an electrically insulative strip having a greater width comprising the steps of: positioning the conductive strip against the insulative strip with the longitudinal edges of the conductive strip spaced from and parallel to the longitudinal edges of the insulative strip; folding two portions of the conductive strip in the same direction against itself along two lines parallel to the longitudinal edges of the conductive strip and spaced apart a distance greater than one-half of the total strip width, whereby a space is defined between facing edges of the fold portions; folding one portion of the insulative strip substantially along one of said two lines against a fold portion of the conductive strip and positioning an edge of said one portion in said defined space; and folding another portion of the insulative strip substantially along the other of said two lines against the other fold portion of the conductive strip and positioning the edge of said other fold portion against the edge of said one fold portion.
 12. The method according to claim 11 further comprising the step of adhering the conductive and insulative strips together. 